Dosimetric models used in the Alpha-Risk project to quantify exposure of uranium miners to radon gas and its progeny

The European project Alpha-Risk aims to quantify the cancer and non-cancer risks associated with multiple chronic radiation exposures by epidemiological studies, organ dose calculation and risk assessment. In the framework of this project, mathematical models have been applied to the organ dosimetry of uranium miners who are internally exposed to radon and its progeny as well as to long-lived radionuclides present in the uranium ore. This paper describes the methodology and the dosimetric models used to calculate the absorbed doses to specific organs arising from exposure to radon and its progeny in the uranium mines. The results of dose calculations are also presented.

Posterior reversible encephalopathy syndrome after solid organ transplantation

BACKGROUND AND PURPOSE

Posterior reversible encephalopathy syndrome (PRES) is known to occur after solid organ transplantation (SOT), potentially associated with cyclosporine and tacrolimus. In this study, we assess the frequency and clinical and imaging characteristics of PRES after SOT.

MATERIALS AND METHODS

We identified 27 patients (13 men and 14 women; age range, 22-72 years) who developed PRES after SOT. Features noted included SOT subtype, incidence and timing of PRES, infection and rejection, mean arterial pressure (MAP), and toxicity brain edema.

RESULTS

PRES developed in 21 (0.49%) of 4222 patients who underwent transplantation within the study period (no significant difference among SOT subtypes). Transplantation was performed in 5 patients before the study period, and 1 patient underwent transplantation elsewhere. In consideration of all 27 patients, PRES typically developed in the first 2 months in patients who had SOT of the liver (9 of 10 patients) and was associated with cytomegalovirus (CMV), mild rejection, or systemic bacterial infection. PRES also typically developed after 1 year in patients who had SOT of the kidney (8 of 9 patients) and was associated with moderate rejection or bacterial infection. Toxicity MAP was significantly lower (P < .001) in liver transplants (average MAP, 104.8 +/- 16 mm Hg) compared with that in kidney transplants (average MAP, 143 +/- 20 mm Hg). Toxicity brain edema was significantly greater (P < .001) in patients who had liver transplants and developed PRES compared with patients who had undergone kidney transplants despite severe hypertension in those who had the kidney transplants.

CONCLUSION

Patients who had undergone SOTs have a similar low incidence of developing PRES. Differences between those who have had liver and kidney transplants included time after transplant, toxicity MAP, and PRES vasogenic edema noted at presentation. In patients who have undergone kidney transplants, severely elevated MAP was associated with reduced, not greater, brain edema.

Evaluation of scattering factor values for internal dose assessment following the IDEAS guidelines: preliminary results

The IDEAS Guidelines for the assessment of internal doses from monitoring data suggest default measurement uncertainties (i.e. scattering factors, SFs) to be used for different types of monitoring data. However, these default values were mainly based upon expert judgement. In this paper, SF values have been calculated for different radionuclides and types of monitoring data using real data contained in the IDEAS Internal Contamination Database. Results are presented.

Avoiding biased estimates of dose when nothing is known about the time of intake

A common problem in internal dosimetry occurs in routine monitoring, when it is required to estimate an intake from a measurement made at the end of a monitoring interval, and the time of intake is unknown. ICRP suggests that it should be assumed that the intake occurred in the middle of the monitoring period. However, it has been shown that this will, in the long-term, lead to biased estimates of a worker's intake and dose. In order to overcome this biasing, the United States Department of Energy (USDOE) recommends a different method based on calculating the intakes for all possible intake times in the interval and then taking an arithmetic average. In a recent paper, it has been shown that both the ICRP and USDOE methods were biased and that the only unbiased estimator of the true intake was obtained by assuming a constant chronic intake throughout the monitoring interval. In all of the analyses carried out to date on this 'Constant Chronic' method, it was assumed that the measurements were exact. In this paper, the effects of assuming either normally or log-normally distributed measurement errors are explored, and the effect on the bias of the intake estimate is investigated.

ERIDAS, a computer program for rapid calculation of internal doses from measurements of people in an emergency

In an emergency involving the deliberate or accidental release of radioactive materials, there could potentially be a large number of people who require monitoring for internal contamination. Doses from these measurements will need to be calculated as quickly as possible. Emergency Response Internal Dose Assessment Software (ERIDAS) has been designed for this purpose.

Cryptococcosis in liver and kidney transplant recipients receiving anti-thymocyte globulin or alemtuzumab

Rabbit anti-thymocyte globulin (ATG) and alemtuzumab have been used for induction or preconditioning and for the treatment of acute rejection in organ transplant recipients in many centers. Such regimens may lead to a substantial decline in the CD4 lymphocyte count to levels seen in other population groups at high risk of cryptococcosis. In view of this, we examined the impact of such therapy on the cumulative incidence of cryptococcosis among liver and kidney recipients. A total of 834 liver and 727 kidney transplants were performed during the study period. Seven hundred and eighty-one patients did not receive ATG or alemtuzumab; 646 received 1 dose of either drug, and 134 patients received 2 doses of either drug. The cumulative incidence of cryptococcosis was 0.26% (2/781) among those who did not receive ATG or alemtuzumab; 0.3% (2/646) among those who received only 1 dose, and 2.24% (3/134) among those who received 2 doses (P=0.03). There were 5 cases of cryptococcosis in liver recipients and 2 in kidney recipients. There were 3 cases of cryptococcal meningitis, 3 of pneumonia, and 1 of disseminated disease. The 2 kidney recipients had meningitis. Diagnosis occurred at a median of 255 days (range 7-517) after transplantation. The mortality rate was 14.2%. We conclude that the use of 1 dose of ATG or alemtuzumab is not associated with an increased cumulative incidence of cryptococcosis, but that those patients receiving 2 doses are at increased risk.

Extended-spectrum beta-lactamase-producing Klebsiella spp. in a neonatal intensive care unit: risk factors for the infection and the dynamics of the molecular epidemiology

The extended-spectrum beta-lactamase (ESBL)-producing Klebsiella spp. cause worldwide problems in intensive care units. The aim of this study was to investigate the molecular epidemiology of ESBL-producing Klebsiella pneumoniae and K. oxytoca strains in a neonatal intensive care unit (NICU) in Budapest, Hungary and to determine the risk factors of the infections and the epidemiological features. Infections with Klebsiella spp. were analyzed retrospectively by reviewing the medical records between January 2001 and December 2005. Antibiotic susceptibility tests, isoelectric focusing, pulsed field gel electrophoresis, plasmid analysis, PCR for bla(TEM) and bla(SHV) and DNA sequencing analysis were performed on ESBL-producing Klebsiella isolates. A total of 45 babies were found to be infected with non-ESBL-producing Klebsiella spp. and 39 with ESBL-producing Klebsiella spp. Of the parameters analyzed, including sex, gestational age, twin pregnancy, birth weight, presence of central vascular catheter, mechanical ventilator use, parenteral nutrition, polymicrobial infection, caesarean section, transfusion and mortality, we found no statistically significant difference between the ESBL and the non-ESBL groups, or between the K. pneumoniae and K. oxytoca species. Further characterization of the ESBL-producing K. pneumoniae and K. oxytoca strains isolated between February 2001 and January 2003 revealed three distinct PFGE patterns of SHV-5-producing K. pneumoniae (A, B, E) and two distinct patterns of SHV-12-producing K. oxytoca (C,D) isolates; these had different plasmid profiles. From July to November 2005, a new SHV-5 producing K. oxytoca (F) was isolated. The molecular epidemiology of ESBL-producing organisms in a NICU over time shows substantial shifts in predominant strains. The ESBL production of the infected organisms has an impact on the survival of newborn babies with infections caused by Klebsiella spp.

Prognostic models in hepatocellular carcinoma (HCC) and statistical methodologies behind them

Hepatocellular carcinoma (HCC) is estimated to be responsible for 250,000 deaths worldwide yearly. Aggressive surgical resection or liver transplantation still remain the only viable curative options for patients suffering the disease despite the multitude of emerging therapies for HCC. However, even with the most aggressive surgical intervention, survival varies widely within each particular stage of HCC. In order to improve utilization of available therapeutic modalities, a number of outcome prognostic models have been developed. This manuscript reviews the prognostic models most commonly utilized in clinical practice and the statistical methodologies on which these models are based. A multitude of statistical and mathematical techniques can be used for prognostic model development. The most common methodologies used for HCC prognostic model development can be generally divided into four groups: survival, artificial neural networks, analysis of variance, and cluster analysis. Survival methodologies (such as Cox proportional hazard model) are commonly employed for estimation of relative significance of risk factors for patient survival or cancer recurrence. Artificial neural networks (such as back-propagation network) can be supreme approximation tools for any continuous or binary function, and as such can be employed for prognostication of HCC recurrence (death). Analysis of variance and cluster analysis are the most common statistical tools of recently evolved microarrays technology, which, in turn, is one of the most promising tools available to the cancer researcher.

Assessment of intakes and doses to workers followed for 15 years after accidental inhalation of 60CO

Intakes and doses are assessed for seven workers who accidentally inhaled particles containing Co in the same incident. Comprehensive whole body data to 15 y, and some early urine and fecal data, are available for each individual. The biokinetic and dosimetric models currently recommended by ICRP have been used to assess these cases. It was not possible to obtain good fits to the data using the ICRP models with their default parameter values. However, good fits to all the measurement data were obtained by varying parameter values following a procedure similar to that recommended in recently developed guidelines for assessment of internal doses from monitoring data. It was found that retention in the lungs was much longer than predicted by the ICRP Human Respiratory Tract Model, and so for each case it was necessary to reduce the particle transport clearance of material from the deep lungs. This reduction in lung clearance rates, and the use of specific AMAD values, were the dominating factors in changing assessed doses from those calculated using ICRP default values.

Adult to adult living-related liver transplant: report on an initial experience in Italy

INTRODUCTION

Living-related liver transplantation has become the treatment of choice for many liver diseases. We present our initial analysis of 53 cases of adult to adult living-related liver transplantation performed in a single institute in Italy.

MATERIALS AND METHODS

From January 2002 to September 2006, we performed 53 adult to adult living-related liver transplantations. The donors (age 18-53) all had genetic or emotional relationships; they were all ABO identical or compatible. Recipients (ages 18-68) suffered from cirrhosis secondary to viral etiology (18), hepatocellular carcinoma with viral cirrhosis (24), cystic fibrosis (2), primary biliary cirrhosis (2), hepatocellular carcinoma with non-viral cirrhosis (2), alcoholic cirrhosis (1), ornithine transcarbamylase deficiency (OTC), (1) criptogenic cryptogenic cirrhosis, (1) primary sclerosing cholangitis, (1) biliary atresia and metastatic carcinoid (1). Donor liver resection resulted in 51 right hepatectomies and two left hepatectomies. Graft body weight ratio was always above 0.8%; graft implantation was performed with the piggy back technique and, in 43 cases, with the use of veno-venous bypass.

RESULTS

There was neither donor mortality nor need of blood transfusion. Actuarial recipient survival rate at 3 years was 82.66% and graft survival rate was 75.34%. Six patients underwent retransplantation: in four cases due to hepatic artery thrombosis, and in two, due to graft dysfunction. Three patients had one episode each of acute cellular rejection.

CONCLUSION

Adult to adult living-related liver transplantation represents a resource to be used in confronting organ shortage, and is a valuable option for decreasing mortality and drop out from the waiting list.

Role of basiliximab in the prevention of acute cellular rejection in adult to adult living-related liver transplantation: a single center experience

We report our single center experience with the use of basiliximab, a chimeric monoclonal antibody directed against the alpha chain of the interleukin-2 (IL-2) receptor (CD25), in combination with a steroid- and tacrolimus-based regimen in adult to adult living-related liver transplantation (ALRLT). Sixty consecutive ALRLTs were analyzed. All patients received two 20-mg doses of basiliximab (days 0 and 4 after transplantation) followed by tacrolimus (0.15 mg/kg/day; 10-15 ng/mL target trough levels) and a dose regimen of steroids (starting with 20 mg iv, switched to po as soon as the patient was able to eat, and weaned off within 1-2 months). Follow-up ranged from 6 to 1699.4 days after transplantation (mean 517.5 days, SD +/- 413.4; median 424 days). Of the recipients, 95% remained rejection-free during follow-up, with an actuarial rejection-free probability of 96.61% within 3 months. Three patients had episodes of biopsy-proven acute cellular rejection (ACR). Actuarial patient and graft survival rates at 3 years were 82.09% and 75.61%. Six patients (10%) experienced sepsis. There was no evidence of cytomegalovirus infections or side-effects related to the basiliximab. We found zero de novo malignancy, although we observed 5 patients with metastatic spread of their primary malignancy during the follow-up. Basiliximab in association with tacrolimus and steroids is effective in reducing episodes of ACR and increasing ACR-free survival after ALRLT.

Coordination of research on internal dosimetry in Europe: the CONRAD project

The EUropean RAdiation DOSimetry Group (EURADOS) initiated in 2005 the CONRAD Project, a Coordinated Network for Radiation Dosimetry funded by the European Commission (EC), within the 6th Framework Programme (FP). The main purpose of CONRAD is to generate a European Network in the field of Radiation Dosimetry and to promote both research activities and dissemination of knowledge. The objective of CONRAD Work Package 5 (WP5) is the coordination of research on assessment and evaluation of internal exposures. Nineteen institutes from 14 countries participate in this action. Some of the activities to be developed are continuations of former European projects supported by the EC in the 5th FP (OMINEX and IDEAS). Other tasks are linked with ICRP activities, and there are new actions never considered before. A collaboration is established with CONRAD Work Package 4, dealing with Computational Dosimetry, to organise an intercomparison on Monte Carlo modelling for in vivo measurements of (241)Am deposited in a knee phantom. Preliminary results associated with CONRAD WP5 tasks are presented here.

IMBA Professional Plus: a flexible approach to internal dosimetry

IMBA (Integrated Modules for Bioassay Analysis) is a suite of software modules that implement the current ICRP biokinetic and dosimetric models for estimation of intakes and doses. The IMBA modules have gone through extensive quality assurance, and are now used for routine formal dose assessment by Approved Dosimetry Services throughout the UK. HPA has continued to develop the IMBA modules. In addition, several projects, sponsored by organisations both in the USA and in Canada, have resulted in the development of customised user-friendly interfaces (IMBA Expert 'editions'). These enable users not only to use the standard ICRP models, but also to change many of the parameter values from ICRP defaults, and to apply sophisticated data handling techniques to internal dose calculations. These include: fitting measurement data with the maximum likelihood method; using multiple chronic and acute intakes; and dealing with different data types, such as urine, faces and whole body simultaneously. These interfaces were improved further as a result of user-feedback, and a general 'off-the-shelf' product, IMBA Professional, was developed and made available in January 2004. A new version, IMBA Professional Plus, was released in April 2005, which is both faster and more powerful than previous software. The aim of this paper is to describe the capabilities of IMBA Professional Plus, and the mathematical methods used.

The autocorrelation coefficient as a tool for assessing goodness of fit between bioassay predictions and measurement data

Project IDEAS has produced guidelines for internal dose assessment. An integral part of this process is assessing the goodness of fit of biokinetic models to bioassay data. It is recommended that a fit should only be accepted if (a) it is close enough to the data not to be rejected by a chi2 test and (b) if it looks acceptable to 'the eye'. The latter criterion was added to enable the assessor to reject fits which seemed to display some sort of systematic bias. However, there are problems with both of these tests: (a) the chi2 test is dependent on the assumed uncertainties which are often unknown, (b) 'by eye' assessment is subjective. In this paper, another statistic, the autocorrelation coefficient of the residuals, rho, is investigated. The main advantages of the rho statistic are that it is objective, very sensitive to biasing and independent of the assumed errors.

Gemcitabine-based transcatheter arterial chemoembolization for unresectable cholangiocarcinoma in thirty-eight patients: Single institutional experience

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Background: Survival for patients with unresectable cholangiocarcinoma is reported to be 5–8 months. Systemic chemotherapy has been disappointing and not shown to significantly improve survival. Transcatheter arterial chemoembolization (TACE) has been shown to prolong survival in hepatocellular carcinoma patients but experience with cholangiocarcinoma is limited. We report our experience with the well-tolerated drug gemcitabine. Methods: Thirty-eight patients with unresectable cholangiocarcinoma were treated with one or more cycles of gemcitabine-based TACE between 2001 and 2005 at our institution. Follow-up imaging was performed on all patients after each TACE procedure. Regimens of TACE included: gemcitabine only (16), gemcitabine followed by cisplatin (2), gemcitabine followed by oxaliplatin (5), gemcitabine and cisplatin (12), and gemcitabine and cisplatin followed by oxaliplatin (3). Actual survival is reported, as 35 of 38 have died from disease (92%). Results: Patients were 57.5 years of age (range 36–87) and a median of 3 treatments (range 1–10) were administered. Median survival from time of first treatment was 10.3 months. Patients receiving gemcitabine followed by cisplatin or oxaliplatin had improved survival (mean 16.5 and 10.5 months respectively) when compared to gemcitabine alone (mean 6 months). Patients receiving gemcitabine and cisplatin as a combination had improved survival (mean 13.4 months) compared to single agent gemcitabine. Patients who progressed on gemcitabine and cisplatin and then received oxaliplatin also showed improved survival (mean 14.3 months) compared to gemcitabine only. Neutropenia, thrombocytopenia and hyperbilirubinemia were the most common toxicities observed. Three patients in the entire series exhibited grade 3 thrombocytopenia while seven patients had grade 3 and one had grade 4 bilirubin levels. Conclusions: This series provides evidence in favor of TACE rather than historically reported alternatives such as systemic chemotherapy or chemotherapy/RT. Our results suggest that gemcitabine based TACE is well tolerated and perhaps best delivered as a combination therapy for patients with unresectable cholangiocarcinoma.

No significant financial relationships to disclose.

A Safe Immunosuppressive Protocol in Adult-to-Adult Living Related Liver Transplantation

BACKGROUND

In this series of 32 adult-to-adult living related liver transplantations, we assessed the efficacy and safety of basiliximab in combination with a tacrolimus-based regimen. Basiliximab, a chimeric monoclonal antibody directed against the alpha chain of the interleukin-2 (IL-2) receptor (CD25), has been extensively evaluated as induction therapy for cadaveric liver transplant recipients.

PATIENTS AND METHODS

Thirty-two adult-to-adult living related liver transplantations were performed in the last 3 years. All patients received two 20 mg doses of basiliximab (days 0 and 4 posttransplantation) followed by tacrolimus (0.15 mg/kg/d; 10-15 ng/mL target trough levels) and steroids (starting with 20 mg IV switched to PO as soon as the patient was able to eat and weaned within 1-2 months). The average follow-up was 395 days after transplantation.

RESULTS

Of the patients, 93.75% remained rejection-free during follow-up with an actuarial rejection-free probability of 92.59% within 3 months. Two patients (6%) had one episode of biopsy-proven acute cellular rejection (ACR). Actuarial patient and graft survival rates at 3 years were 86.85% and 81.25%. One patient (3%) experienced one episode of sepsis. There was no evidence of cytomegalovirus infections or side effects related to the basiliximab. We found zero de novo malignancy but we observed two patients with metastatic spread of their primary malignancy during the follow-up.

CONCLUSION

Basiliximab in association with tacrolimus and steroids is effective as prophylaxis of ACR among adult living related liver transplant recipients.

Obtaining an unbiased estimate of intake in routine monitoring when the time of intake is unknown

A common problem in internal dosimetry occurs in routine monitoring, when it is required to estimate an intake from a measurement made at the end of a monitoring interval, and the time of intake is unknown. ICRP suggests that, in these cases, it should be assumed that the intake occurred in the middle of the monitoring period. However, it has been shown that this will, in the long term, lead to biased estimates of a worker's intake and dose. In order to overcome this biasing, the United States Department of Energy (USDOE) recommends a different method based on calculating the intakes for all possible intake-times in the interval, and then taking an arithmetic average. In this paper, it is shown that both the ICRP and USDOE methods are biased. An alternative method is suggested, which assumes a constant chronic intake throughout the monitoring interval. Monte Carlo simulations are used to estimate the magnitude of bias for two realistic monitoring programmes using all three methods. It is shown that the proposed method is unbiased and also yields estimates of intake that are generally closer to the actual intake, than the other two. The Monte Carlo conclusions are backed up by a theoretical analysis of bias. Finally, the source of bias in the apparently intuitive approach of the USDOE method is revealed by viewing the problem from a Bayesian perspective.

IMBA Expert: internal dosimetry made simple

In 1997, a collaboration between British Nuclear Fuels plc (BNFL), Westlakes Research Institute and NRPB started, with the aim of producing IMBA (Integrated Modules for Bioassay Analysis), a suite of software modules that implement the new ICRP models for estimation of intakes and doses. This was partly in response to new UK regulations, and partly due to the requirement for a unified approach in estimating intakes and doses from bioassay measurements within the UK. Over the past 5 years, the IMBA modules have been developed further, have gone through extensive quality assurance, and are now used for routine dose assessment by approved dosimetry services throughout the UK. More recently, interest in the IMBA methodology has been shown by the United States Department of Energy (USDOE), and in 2001 an ambitious project to develop a software package (IMBA Expert USDOE Edition) which would meet the requirements of all of the major USDOE sites began. Interest in IMBA Expert is now being expressed in many other countries. The aim of this paper is to outline the origin and evolution of the IMBA modules (the past); to describe the full capabilities of the current IMBA Expert system (the present) and to indicate possible future directions in terms of capabilities and availability (the future).

UK laboratory intercomparison on internal dosimetry

A laboratory intercomparison for internal dose assessment from a variety of intake scenarios is described. This is the first UK intercomparison using the revised ICRP Human Respiratory Tract and biokinetic models. Four United Kingdom laboratories participated and six cases were assessed. Overall, the agreement in internal dose assessments between laboratories was considered satisfactory with 79% of the assessed committed effective doses, e(50), for cases within a band of +/- 40% of the median value. The range (highest/lowest) in e(50) estimated by the laboratories was smallest (1.2) for a case involving inhalation of 137Cs. The range was greatest (6.0) for a case involving a wound with, and possible inhalation of, 238Pu, 239Pu and 241Am; the variation between laboratories in assessment of intakes could not be considered to be satisfactory in this case. Judgements on the most appropriate data to use in estimating intakes, choice of parameter values for use with the ICRP models and allowing for the effects of treatment with DTPA were important sources of variability between laboratories.

Experimental determination of the absorption rate of unattached radon progeny from respiratory tract to blood

An exposure methodology was developed for the determination of the absorption rate of unattached radon progeny deposited in the human respiratory tract to blood. Twenty-one volunteers were exposed in a radon chamber during well-controlled aerosol and radon progeny conditions, with predominantly unattached radon daughters. Special efforts were made to restrict the dose to the volunteers to an absolute maximum of 0.08 mSv. Measurements of radon gas and radon progeny in blood samples of these volunteers indicated absorption half times of 20 min to 60 min. Former determinations, mainly performed with much larger aerosol particles of diameters between 100 nm and 1,000 nm, implied absorption half times around 10 h. This indicates that the absorption of radon decay products from ciliated airways into blood is dependent upon particle size and particle composition.

Uncertainty analysis of the weighted equivalent lung dose per unit exposure to radon progeny in the home

A parameter uncertainty analysis has been performed to derive the probability distribution of the weighted equivalent dose to lung for an adult (w(lung) H(lung)) per unit exposure to radon progeny in the home. The analysis was performed using the ICRP Publication 66 human respiratory tract model (HRTM) with tissue weighting factor for the lung, w(lung) = 0.12 and the radiation weighting factor for alpha particles, wR = 20. It is assumed that the HRTM is a realistic representation of the physical and biological processes, and that the parameter values are uncertain. The parameter probability distributions used in the analysis were based on a combination of experimental results and expert judgement from several prominent European scientists. The assignment of the probability distributions describing the uncertainty in the values of the assigned fractions (ABB, Abb, AAI) of the tissue weighting factor proved difficult in practice due to lack of quantitative data. Because of this several distributions were considered. The results of the analysis give a mean value of w(lung) H(lung) per unit exposure to radon progeny in the home of 15 mSv per working level month (WLM) for a population. For a given radon gas concentration, the mean value of w(lung) H(lung) per unit exposure is 13 mSv per 200 Bq.m(-3).y of 222Rn. Parameters characterising the distributions of w(lung) H(lung) per unit exposure are given. If the ICRP weighting factors are fixed at their default values (ABB, Abb, AAI = 0.333, 0.333, 0.333; w(lung) = 0.12; and wr = 20) then on the basis of this uncertainty analysis it is extremely unlikely (P approximately 0.0007) that a value of Hw/Pp for exposure in the home is as low as 4 mSv per WLM, the value determined with the epidemiological approach. Even when the uncertainties in the ABB, Abb, AAI, values are included then this probability is predicted to be between 0.01 to 0.08 depending upon the distribution assumed for describing the uncertainties in the ABB, Abb, AAI, values. Thus, it is concluded that the uncertainties in the HRTM parameters considered in this study cannot totally account for the discrepancy between the dosimetric and epidemiological approaches.

Modified temporary end-to-side portocaval shunt in liver and small bowel transplantation

Piggyback orthotopic liver transplantation (LTx) has permitted the elimination of extra-corporeal venovenous bypass. In some instances, an internal temporary portocaval shunt has to be constructed in order to prevent hemodynamic instability. We describe a technique in which a donor iliac vein graft is used to bridge the distance between the portal vein and vena cava in cases where a direct shunt cannot be constructed. This technique can be applied to liver Tx as well as to liver and small bowel Tx.

Hepatocellular carcinomas in native livers from patients treated with orthotopic liver transplantation: biologic and therapeutic implications

The gross and histopathologic characteristics of 212 nonfibrolamellar hepatocellular carcinomas (HCCs) discovered in native livers removed at the time of liver transplantation were correlated with features of invasive growth and tumor-free survival. The results show that most HCCs begin as small well-differentiated tumors that have an increased proliferation rate and induce neovascularization, compared with the surrounding liver. But at this stage, they maintain a near-normal apoptosis/mitosis ratio and uncommonly show vascular invasion. As tumors enlarge, foci of dedifferentiation appear within the neoplastic nodules, which have a higher proliferation rate and show more pleomorphism than surrounding better-differentiated areas. Vascular invasion, which is the strongest predictor of disease recurrence, correlates significantly with tumor number and size, tumor giant cells and necrosis, the predominant and worst degree of differentiation, and the apoptosis/mitosis ratio. In the absence of macroscopic or large vessel invasion, largest tumor size (P <.006), apoptosis/mitosis ratio (P <.03), and number of tumors (P <.04) were independent predictors of tumor-free survival and none of 24 patients with tumors having an apoptosis/mitosis ratio greater than 7.2 had recurrence. A minority of HCCs (<15%) quickly develop aggressive features (moderate or poor differentiation, low apoptosis/mitosis ratio, and vascular invasion) while still small, similar to flat carcinomas of the bladder and colon. In conclusion, hepatic carcinogenesis in humans is a multistep and multifocal process. As in experimental animal studies, aggressive biologic behavior (vascular invasion and recurrence) correlates significantly with profound alterations in the apoptosis/mitosis ratio and with architectural and cytologic alterations that suggest a progressive accumulation of multiple genetic abnormalities.